Conventionally, in a bladder type tire vulcanizing apparatus, for example, an expandable and contractable bladder made of a material having elasticity (for example, butyl rubber) is introduced inside a raw tire, the bladder and the raw tire are accommodated in a mold by mold clamping, and a heated and pressurized medium, such as water vapor or nitrogen gas, or the like, at high temperature and high pressure is supplied into the bladder, thereby causing the bladder to expand and make tight contact with the inner surfaces of the raw tire. The introduction time of the water vapor in the initial period at the start of vulcanization and the introduction time of the nitrogen gas in the latter period of the vulcanization process, and the like, are set appropriately in such a manner that the internal temperature of the raw tire, in other words, the internal temperature of the bladder becomes a desired temperature. In this state, the raw tire is pressed against the inside of the mold by the expanding force of the bladder while the interior of the raw tire (the interior of the bladder) is held at a desired temperature and pressure. The raw tire is then vulcanized and molded by holding this state until a desired vulcanizing reaction has progressed and completed from the outer side through to the inner side of the raw tire.
Here, the technology disclosed in Patent Document 1 is one technology relating to a tire vulcanizing apparatus such as that described above. This prior art technology is described below.
Patent Document 1 discloses technology relating to a tire vulcanizing apparatus in which a heating and pressurizing medium which is replenished into the interior of a bladder and the replenished medium is heated by means of the heating and pressurizing medium expelled from the bladder after the vulcanization and molding of a raw tire. The tire vulcanizing apparatus disclosed in Patent Document 1 comprises: a preheater which preheats a heating and pressurizing medium for vulcanizing and molding a raw tire, a hot/cool separating device which extracts the hot component of the heating and pressurizing medium by using the pressure energy of the heating and pressurizing medium which is expelled from the bladder after vulcanizing and molding a raw tire, and a heat exchanger which heats the heating and pressurizing medium replenished into the bladder by heat exchange with the aforementioned hot component. Furthermore, Patent Document 1 discloses technology which aims to achieve a uniform pressure of the heating and pressurizing medium that flows inside the bladder by providing a pressure gauge to the upstream side of the preheater. By means of this technology, it is possible readily to raise or lower the filling amount of the high-pressure heating and pressurizing medium which is replenished into the bladder, and consequently Patent Document 1 states that it is possible to stabilize the pressure of the heating and pressurizing medium inside the raw tire.
However, in the tire vulcanizing apparatus described in Patent Document 1, for example, if water vapor is used as the heating and pressurizing medium which is supplied into the bladder, in other words, into the raw tire, then there are cases where it is not possible to obtain a desired water vapor pressure due to the relationship between the saturated water vapor pressure and the saturation temperature. For example, if the type of tire being vulcanized has a compound which it is wished to vulcanize at low temperature (a type of rubber used in the ground-contacting surface of the tire), or the like, then it is possible to lower the temperature inside the bladder by reducing the supply pressure of the water vapor forming the heating and pressurizing medium. However, in this case, the water vapor supply pressure falls and consequently it becomes impossible to press the raw tire sufficiently against the inner surfaces of the mold. Consequently, the application of the intended design to the outer surface of the tire, in other words, the transfer of a pattern to the outer surface of the tire is insufficient and therefore defects occurs in the outer appearance of the tire.
Furthermore, the tire vulcanizing apparatus according to the prior art includes problems such as air blockages. These air blockages give rise to defects in the external appearance of the tire and tire molding defects due to insufficient expulsion to the exterior of the tire of the air present between the inner surfaces of the mold and the outer surfaces of the raw tire and between the inner surfaces of the raw tire and the outer surface of the bladder, the air present inside the raw tire, or the reaction gas generated during the vulcanization reaction, as a result of insufficient pressing force of the bladder pushing the raw tire against the inner surfaces of the mold.
Furthermore, since the raw tire is constituted by joining together or bonding together various members, then the tensile strength of the members is not necessarily uniform in the outer circumferential direction and breadthways direction of the tire. Consequently, if the pressure inside the bladder, in other words, the pressure inside the internal space of the raw tire, rises suddenly after the raw tire has been mounted in the mold, then the expansion of the raw tire in the outer circumferential direction does not occur uniformly and as a result of this, problems arise in that the uniformity of the tire, such as the tire balance, declines. Another possible way of avoiding this problem is to increase the time period of the pressure rise of the heating and pressurizing medium, but in this case, the rise in the internal temperature of the bladder becomes slower and therefore the vulcanization and molding time becomes longer, leading to other problems, such as decline in productivity.    [Patent Document 1] Japanese Patent Application Publication No. 2005-22399